Plain-weave unidirectional stretch fabric



Oct. 8, 1968 N. c. PIERCE 3,404,710

PLAIN-WEAVE UNIDIRECTIONAL STRETCH FABRIC Filed July 14, 1966 STRETCH DIRECTION YARNS: FILAMEIITS- NONELASTDNERIC. ORDERED HELICAL CRINIP. CRIMP FREQUENCY OF 20 PER INCH OR NDRE. & CRINIP DEVELOPMENT UP AT LEAST 25%.

NOIISTRETCH DIRECTION YARNS: NDNELASTDMERIC AND DCCURRINC AT I.5 T0 3 TIMES THE CRIHP FREQUENCY OF THE FILAHENTS IN THE STRETCH DIRECTION YARNS.

'INVENTOR NDRYIIN C. PIERCE ATTORNEY United States Patent PLAlN-WEAVE UNIDIRECTIONAL W STRETCH FABRIC Norwin C. Pierce, Greenville, NC, assiguor to E. I. du

Pont de Nemours and Company, Wilmington, Del., a

corporation of Delaware Filed July 14, 1966, Ser. No. 565,072 8 Claims. (Cl. 139---421) ABSTRACT OF THE DISCLOSURE A tightly-woven, plain-weave, flat textile fabric having a stretch in one direction of 20% to 100% which retracts to substantially the original dimension upon release of tension, the stretch-direction yarns being com posed of non-elastomeric thermoplastic filaments having an ordered helical crimp, a Crimp-Frequency of at least 20 crimps per inch and a Crimp Development of at least 25%, the yarns in the other fabric direction occurring at a yarn frequency of 1.5 to 3 times the filament crimp frequency in the stretch-direction yarns and being non-elastomeric textile yarns selected from the group consisting of continuous-filament thermoplastic yarn and spun yarn of at most 20/ 1 cotton count linear density. Also disclosed is a process for producing the above stretch fabric.

This invention relates to woven textile fabrics, and, more particularly, to lightweight stretch-fabrics comprising synthetic non-elastomeric textile yarns.

Considerable commercial interest exists today in fabrics which possess the ability to stretch and recover to their original size.

Problems attending the use of conventional stretch fibers such as rubber in these fabrics has led researchers to seek other fibers as substitutes. The adaptation of synthetic linear condensation filaments such as polyethylene terephthalate and polyhexamethylene adipamide to confer a high degree of stretch to tightly woven fabrics would meet with considerable commercial success, because such filaments possess outstanding properties such as high-strength, dimensional stability, pleasing aesthetic qualities and good resistance to abrasion and atmospheric conditions. However, fabrics prepared from such filaments to provide high degrees of recoverable stretch in flat, lightweight, tightly woven fabric constructions, such as broadcloths and taffetas, were unknown prior to the present invention.

This invention provides a lightweight, tightly woven textile fabric which possesses at least 20% and as high as 60 to 100% stretch. Another provision is a highstretch, tightly woven fabric which has essentially no puckered appearance whatsoever. A further provision is a stretch-fabric which possesses the fabric aesthetics and appearance common to shirting fabrics. Other provisions will become apparent hereinafter.

The stated advantages of this invention are achieved by a fiat, tightly woven, plain-weave, stretch-fabric of non-elastomeric textile yarns of which the yarns are of thermoplastic filaments having an ordered helical crimp (e.g., either crimped composite-filament textile yarn or torsionally-crimped textile yarn) characterized by a Crimp Frequency of at least 20 crimps per inch (8 crimps per cm.) and a Crimp Development of at least 25% which provide a fabric stretch of 20% to 100%. The yarns in theother fabric direction are from the group consisting of. continuous-filament thermoplastic textile yarn or spun yarn of at most about 20/1 cotton count linear density, and occur in the fabric at a frequency which is about 1.5 to 3 times the filament crimp frequency of the yarns in the stretch direction of the fabric.

3,404,710 Patented Oct. 8, 1968 ice The significance of this fabric may be appreciated by visualizing a fabric, similar in appearance and aesthetics to those fabrics commonly used for dress shirts and petticoats, but having 20% to 60% or more stretch in one fabric direction. 1

By a flat fabric is meant a fabric which exhibits no buckled, puckered, or crepe-like appearance.

By a stretch fabric is meant a fabric having at least 20% stretch and which, upon release of stretch-inducing force, retracts substantially to its original dimensions. The following procedure is used herein to measure percent stretch:

A sample of the fabric to be tested is cut to 21 inches (54 cm.) in its stretch direction and 2.25 inches (5.7 cm.) in its non-stretch direction. The two lengthwise edges of the fabric sample are ravelled until the fabric is 2.0 inches (5.1 cm.) wide; bench-marks 50 cm. apart (L are placed .along the length of the specimen, a load of 4.0 lbs. (1814 gms.) is applied to its stretch direction and the average length (L between bench-marks is calculated. The stretch of the fabric is calculated by the formula:

Stretch (percent)= This invention is concerned with tightly woven fabrics such as broadcloths and taffetas. Conventionally used counts for such fabrics generally range from 76 to 110 warp ends per inch (30 to 43 warp ends per cm.) and from 64 to picks per inch (25 to 35 picks per cm.).

The fibers used in the stretch direction of the new fabrics have an orderedhelical crimp, characterized by a Crimp Frequency of at least 20 crimps per inch (8 crimps per cm.) with a crimp development of at least 25 Preferably the yarn has a Crimp Frequency of 35 to 40 crimps per inch (14 to 16 crimps/cm.) and is used as filling in a fabric having 60 to 110 warp ends per inch. The term Crimp Frequency may be understood by reference to the following analytical procedure, used to measure this property in the fibers described herein:

The test yarn is exposed to 250 F. (121 C.) dry heat for 5 minutes while under a load of 1.5 mg./denier. Fibers are removed from the yarn, loaded with a 0.1- gramper denier load and one-inch (2.54-cm.) benchmarks are made on the fibers. The fibers are then relaxed just enough to allow visual observation of the crimps. The average number of peaks per marked interval protruding from one side of the axis of the fiber, the axis being a straight line from end-to-end, is the Crimp Frequency of the fiber.

In addition to the Crimp Frequency characteristics, the stretch-direction yarns of the new fabrics must possess a Crimp Development of at least about 25% and preferably at least 50%. The term Crimp Development is used to describe the tendency of a yarn to crimp while under load. The procedure used to measure the Crimp Development of the crimped yarns described herein is as follows:

The test yarn is wound on a reel at a tension sufiicient to keep the yarn taut at all times (preferably at about 0.1 gram/denier) until the denier is 1500'. The yarn is then removed from the reel, hung on a hook and a 4.5-gram weight is suspended from the bottom of the loop. The loop is then immersed into boiling water for 15 minutes. The loop is removed and dried overnight with the 4.5- gram weight remaining suspended from the loop. The crimped length is then measured (L The 4.5-gram weight is replaced by a 300-gram weight and the length of the loop is again measured (L Crimp Development is calculated by the following formula:

Crimp Development (percent) X 100 Preferably, the stretch-direction yarns of the new fabrics of this invention are polyester composite-filament yarns. Such yarns are composed of filaments that have at least two separate and distinct polymeric species in intimate adherence and in side-by-side relationship along their length. Some yarns of this type are disclosed in Breen U.S. Patent No. 3,038,236, dated June 12, 1962. Preferably poly(trimethylene terephthalate) is used for one component and poly(ethylene terephthalate) is used for the other component, the components being in the ratio of from about 40/60 to 60/ 40, and the yarn is spun in the general range of from 500 to 750 y.p.m. (760 to 1140 cm./sec.), drawn in the range of from 3.5 to 5 times its original length, and annealed at temperatures in the range of from 145 to 185 C., to obtain the yarn characteristics essential to the invention and disclosed hereinabove.

Torsionally crimped yarns may also be used in the stretch direction of the new fabrics. Torsionally crimped yarns are those yarns which, in processing, are twisted, heat-set in their twisted configuration, and untwisted. Commercially known processes, such as the Superloft (trademark of Leesona Corp.), Fluflon (trademark of Fluflon Ltd.), and Helanca (trademark of Heberlein and Co.) processes, can be used to make torsionally crimped yarns which are suitable for use in accordance with this invention. As illustrated in Example III, a suitable torsional crimp can be imparted to a 70-denier polyester yarn with the Superloft process by falsetwisting the yarn approximately 80 turns per inch (31 turns per cm.), overfeeding about 8%, and heat-setting at about 232 C. Appropriate conditions for 6,6-nylon yarn are illustrated in Example IV.

It will be realized that few yarns exist today which possess the characteristics necessary for the yarns used in the stretch direction of the new fabrics provided herein. Accordingly, it will be recognized that as yarns possessing these characteristics appear in the trade, it will be obvious to apply them to the teachings of this specification.

Any continuous-filament thermoplastic textile fiber may be used in the non-stretch direction of the fabrics of this invention. Thus, polyesters, particularly polyethylene terephthalate and copolymers thereof, and polyamides, particularly polyhexamethylene adipamide and copolymers thereof are among the fibers which may be used. Polyethylene terephthalate is preferred because of the excellent wash-wear and aesthetic properties of fabrics woven therefrom. These yarns may be from about 30 to about 250 denier and from about 3 to about 50 filaments.

Spun yarns comprising natural fibers such as cotton, rayon, and wool and synthetic fibers such as polyamide, acrylic, and polyester, or blends of any of these products, may also be used in the non-stretch direction provided that they have a linear density of about 20/1 cotton count or finer.

The special relationship of the Crimp Frequency of the stretch-direction yarns to the frequency of occurence of the non-stretch direction yarns in the new fabrics is essential to the invention. Accordingly, and subject to the Crimp Frequency and Crimp Development limitations for the stretch-direction yarns of the new fabric as stated hereinabove, the frequency of occurrence of the nonstretch yarns in the fabric must be from 150% to 300% and is preferably about 200% of the Crimp Frequency of the stretch-direction yarns. T 0 illustrate, if yarn of 50 crimps per inch (20 crimps/cm.) Crimp Frequency is used for the fabric filling, the number of wrap ends per inch in the fabric must be from 75 to 150 (30 to 60/cm.) and preferably about 100 (40/cm.).

The frequency of occurrence of the non-stretch yarns in the fabric refers to the number of ends per inch in unfinished fabrics, i.e., before the fabric is exposed to high temperatures of the order of at least about 80 C. as are used by convention in scouring, dyeing or heat-setting operations. Of course, after the fabrics are exposed to such high temperatures, the wrap yarns may occur at a higher frequency in the fabric than before such operations.

The advantages of this invention are fully realized in closely woven flat fabrics such as talfetas and broadcloths. The finished construction of the taffeta and broadcloth fabrics of this invention may be any construction used today, subject, of course, to the aforementioned Crimp Frequency and Crimp Development limitations of the yarns in the stretch direction.

This invention is further illustrated by the following examples of preferred embodiments, although it is to be understood that the invention is not limited thereto.

The relative viscosity (RV) of the poly(ethylene terephthalate) stated in the examples in the ratio of the viscosity of a 10% solution of the poly(ethylene terephthalate) in a mixture of 10 parts of phenol and 7 parts of 2,4,6-trichlorophenol (by weight) to the viscosity of the phenol trichlorophenol mixture, per se, measured in the same units at 25 C.

Intrinsic viscosity as used therein is defined as the limit of the fraction as concentration 0 approaches zero, where r is the relative viscosity measured in the manner indicated above, except that the relative viscosity is measured at several concentrations to facilitate extrapolation to zero concentration and the solvent employed in this measurement is a mixture of three parts of methylene chloride and one part of trifluoroacetic acid (by weight).

Brief description of the drawing:

The drawing shows the wrap cross-section of a stretch fabric of this invention. The yarn characteristics in the stretch direction and the nonstretch direction are designated.

EXAMPLE I This example illustrates the critical importance of the relationship between crimp-frequency of the stretch-direction yarns and the frequency of occurrence of the nonstretch direction yarns in fabrics and shows the high percent stretch attained in fabrics of this invention as compared to a fabric of the prior art.

Four filling yarns are produced as follows:

Yarn A A 35-denier/25-filament bicomponent yarn is prepared by melt-spinning, at approximately 277 C., poly(trimethylene terephthalate) of 1.6 intrinsic viscosity and poly(ethylene terephthalate) of 24 RV in a weight ratio of /50 with a 25-hole spinneret similar to that disclosed in FIGURE 14 of US. Patent No. 3,117,362. The filaments are withdrawn from the spinneret at 700 yards per minute (1040 cm./sec.), drawn at 93 C. to 3.7 times their original length and annealed at 185 C. The yarn has a Crimp Development of 62% and a Crimp Frequency of 47 crimps per inch (18.5/cm.). Two ends of this yarn are plied 3-turns-per-inch twist (1.2/cm.) to give a total of 50 filaments in the final yarn bundle.

Yarn B The procedure is the same as above with the exceptions that a 34-hole spinneret is used, the polyethylene terephthalate is 21 R.V., and the yarn is spun at a temperature of approximately 295 C. at 533 yards per minute (814 cm./sec.) and drawn to 4.8 times its original length, giving a final denier of 70 instead of 35. The final yarn is 2.06 denier per filament, has a Crimp Development of and a Crimp Frequency of 42 crimps per inch (l6.5/cm.). This yarn is not plied but is twisted 3 turns per inch (ll/cm.),

3,404,710 5 6 Yarn C picks per inch (31/cm.); fabric is jig-scoured, jigbleached and dried at 250 F. (121 C.). The procedure is the same as for Yarn A with the exceptions that the yarn is spun at a temperature of ap- .i 2 5 gfi g i i g ga a proximately 295 C. at 547 yards per minute (832 cm./ pm S per mc a me c u e lg bleached, and dried at 250 F. (121 C.). sec.) and drawn to 4.7 times its original length giving a l I h fi h d d h final denier of 70 instead of 3s. The final yarn is 2.80 Tab 6 I s Ows e constructlo an erties of the fabrics. It is clearly shown that fabrics in 23 2 2 332? giz f' gg g g gggg :2 5: 5 which the loom construction of the warp lies within the (14/cm.). This yarn is neither plied nor twisted. range of from about 150 to 9 of the Crimp 1O quency of the filling yarns (Fabrics 1, 2, 3 and 4) possess Yam D good levels of stretch even when subjected to various The procedure is the same as for Yarn 'C with the finishing sequences; whereas a fabric (Fabric 5) not meetexceptions that a 15-hole spinneret is used, the yarn is ing the specifications taught herein exhibits no significant spun at a temperature of approximately 290 C., the stretch.

TABLE II Loom construction, Warp yarn ends/ Finished construction, Fabric warp x fill inchXlOO divided warp x fill stretch Fabric by filling yarn (filling Per inch Per cm. crimp frequency For inch Per cm. directioit),

percen 66 X 108 26 X 43 194 108 X 117 43 X 46 76 X 98 30 X 39 224 148 X 104 58 X 41 86 X 88 34 X 35 253 137 X 91 54 x 36 36 96 X 78 38 X 31 282 137 X 82 54 X 33 126 X 48 50 X 19 370 154 X 53 61 X 21 polyethylene terephthalate is R.V., and the yarn is EXAMPLE III 4.67 denier per filament, has a Crimp Development of 68% and a Crimp Frequency of 26 crimps per inch This example illustrates the use of torsionally crimped (10/cm.). This yarn is twisted 3 turns per inch (l.2/cm.). yams accordance Wlth the Present mventlon- The warp yarn is commercially available 34-filament StaPdard 26 R P Y( y rcphthalate) 1S meltpoly(ethylene terephthalate) of 2.06 denier per filament. Spur} m conventlopal 9 70' den1er/ 34'filament Filling yarns A through D are separately woven with Tf'rslonal Crlmp 1s linparted 3 the Y by the warp yarn toa series of four plain-weave fabrics of the supefloft Process' In Superloft Process: the 96 warp ends per inch by 76 picks per i h The f b i yarn is twisted to 83 turns per inch (33.5/cm.), overfed are jigscoumd and frame dried at Wet width at a term to 8%, and heat-set at 232 C. while in its twisted conperature f 250 F, 121" Table I shows the figuration. In the twisting step, some of the yarn is twisted structions and stretch-properties of the finished fabrics. in direction and the remailfdel" is twisted in the Fabrics A to C are in conformity with the invention. dlrectloll- The Y has a CflmP D pment Of It is readily seen that Fabric D, comprised of the 0 and a Crimp Frequency of 28 crimps per inch 4.67-denier yarn, being in discord with the teachings (11/cm.).

herein, exhibits an insignificant degree of stretch. The torsioiially crimped yarn is used as the filling, al-

TABLE I Warp yarn, Filling yarn, I ends/inchX 7 Fabric stretch Fabric denier per Filling yarn crimp 100 divided Finished fabric construc- (filling filament frequency by filling yarn tion, warp ends per inch/ direction),

crimp Ire- 7 picks per inch percent quency 1 1. 40 47/ii'i. 204 184 (73/cm.)/80 (3l/cin.) 66 2. 06 42/in. 229 142 (56/ern.)/84 (33/cm.). 38 a 2.80 35/111. 274 136.(54/cm.)/80 (31/Cm.) 21 4. 67 26/in 369 120 (48/cm.)/82 (32/oin.). l4

1 Loom construction, 96 ends/inch (38/crn.) by 76 picks/inch (30/cm.).

EXAMPLE II ternating 2 picks S twist 2 picks Z twist, in four plain- This example further illustrates the principle shown in gg s j gi i E i g; g T: 21 g 3;

n u n n 4 Example I in fabrics of constant Crimp Frequency filling p y o X mp e e O m ns c n the fabrics is as follows yarn and various warp end frequencies.

Fabric ].--66 warp ends per inch (26/cm.) by 108 Flve plan-Mamie faimcs are produced each compns- 0 picks per inch (43/cm.); fabric is batcher-tank scoured, mg a Warp. yam ldeimcal to the Warp yam of Examp jig-scoured 'ig-bleached and dried at 250 F (121 C) I and a. filling yarn similar to ,Yarn B of Example I but J Fabric 2.86 warp ends per inch (34/cm.) by 88 gsgii ggg ii z gg s 225 352: Loom constructions a picks per inch (35 /cm.); fabric is stick-scoured, beck- Fabric 1 6 W rp ends p i (26mm) and 108 i i i fc e v vg rg 2335 225 i ricfi gs jcrhg by a picks per inch (43/cm.); fabric is batcher-tank scoured, picks per inch (31 /cm fabric is scoljred jig-scoured, jig-bleached, and dried at 250 F. (121 C.). bleached and dried at 2 F (1210 1g .Fabric warp ends in.ch (30mm) and 98 Fabric 4--126 warp ends per inch 50/cm) by 48 picks per inch (39/c m.); fabric is jig-scoured, dried, Napicks per inch (19 /cm fabric is jig scou'red j tional Hot Roll heat-set at 350 F. (188 C.) (20 sec.), i

V o o bleached, and dried at 250 F. 121 C.). ]1g'bleached and dned at 250 (121 Table III shows the construction and stretch properties Fabric 3.--86 warp ends per inch (34/cm.) and 88 v of these fabrics. Fabrics 1 and 2 are in accordance with PICKS P Inch fabric 15 stlckscoured, beckthis invention. Fabrics 3 and 4, which do not have the scoured, beck-bleached, and dried at 250 F. (121 C.). filling yarn Crimp Frequency-warp end frequency rela- Fabric 4.96 warp ends per inch (38/cm.) and 78 tionship taught herein, exhibits no significant stretch.

TABLE III Loom construction, Warp yarn ends/ Finished construction, Fabric warp x fill inchXlOO divided warp x fill stretch Fabric by filling yarn (filling Per inch Per cm. crimp frequency For inch lcr em. direction),

percent 66 X 108 26 X 43 236 128 X 120 50 X 47 64 86 X 88 34 X 35 307 121 X 95 48 X 37 20 96 X 78 38 x 31 343 110 X 83 43 X 33 126 X 48 50 X 19 450 143 X 53 56 X 21. 10

EXAMPLE IV 10 This invention provides flat, plain-weave, tightly woven This example illustrates the invention as applied to fabrics of synthetic linear polyamides.

Standard 70-denier/34-filament 6,6-nylon yarn is crimped by the Superloft process, the yarn being twisted 76 turns per inch (30/cm.), overfed to 4.3%, and heat-set at 230 C. while in its twisted configuration. The yarn has a Crimp Development of 24% and a CrirnpEFrequency of 31 crimps per inch (12/ cm.).

The torsionally crimped yarn is used as the filling in three plain-weave constructions, the warp yarns of which are identical to the warp yarns of Example I. The loom construction of these fabrics is as follows:

Fabric 1.60 warp ends per inch (24/cm.) by 112 picks per inch (44/ cm.);

Fabric 2.72 warp ends per inch (ZS/cm.) by 100 picks per inch (39/cm.);

Fabric 3.96 warp ends per inch (BS/cm.) by 76 picks per inch (30/crn.).

The fabrics are crab-scoured, jig-scoured, jig-bleached, and dried at 250 F. (121 C.).

Table IV shows the fabric constructions and stretch properties. The critical relationship between the crimpfrequency of the stretch-direction yarns and the frequency of non-stretch yarns in the fabric is clearly shown.

TABLE IV textile fabrics which possess not only desirable textile aesthetic properties but the unique advantage of being highly stretchable to an extent heretofore unknown in p such fabrics. I

A further advantage of these stretch fabrics is in their processing. Unlike elastomers, the yarns used in the practice of this invention possess surface-friction characteristics which facilitate rather than retard weaving operations.

These advantages make the new fabrics highly desirable for wearing apparel and home furnishings.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. A tightly-woven, plain-weave, flat textile fabric having a stretch in one direction of to 100% which retracts to substantially the original dimension upon release of tension, the stretch-direction yarns being composed of non-elastomeric thermoplastic filaments having an ordered helical crimp, a Crimp Frequency of at least 20 crimps Loom construction, Warp yarn, ends/ Finished construction, Fabric warp x fill inchXlOO divided warp x fill stretch Fabric by filling yarn A (filling Per inch Icr cm. crimp frequency For inch Icr cm. direction),

percent 60 x 112 24 x 44 194 96 x 131 38 X 52 46 72 X 100 28 x39 232 100 x 109 40 x 43 28 96 x 76 38 x 310 116 X 80 46 x 31 13 EXAMPLE V per inch and a Crimp Development of at least 25 the Two 63-denier/l7-filament polyamide yarns comprising filaments prepared from a polyamide which is the reaction product of bis(4-aminocyclohexyl)methane and dodecanedioic acid and crimped by the Superloft process; Yarn A being twisted 77 turns per inch (30.3/cm.), underfed to 4.5%, and heat-set at 202 C. while in its twisted configuration; Yarn B being twisted 60 turns per inch (23.6/cm.), underfed to 4.5 and heat-set at 210 C. while in its twisted configuration. Yarn A has a Crimp Frequency of 29 crimps per inch (11.4/cm.) and Yarn B has a Crimp Frequency of 18 crimps per inch (7.1/ cm.).

Yarn A is 2-plied and used as the filling in a plain weave fabric (Test Fabric) of 60 warp ends per inch (24/cm.) by 66 picks per inch (25.9/cm.) loom construction.

Yarn B is 2-plied and used as the filling in another fabric (Control Fabric) of the same loom construction.

The warp yarn of each fabric is a standard 26/1 cc. poly(ethylene terephthalate)/cotton (65/35) blend. Each fabric is batcher-tank scoured and dried at approximately 120 C.

Table V shows the stretch properties of each fabric.

yarns in the other fabric direction occurring at a yarn frequency of 1.5 to 3 times the filament crimp frequency in the streach-direction yarns and being non-elastomeric textile yarns selected from the group consisting of continuous-filament thermoplastic yarn and spun yarn of at 0 most 20/1 cotton count linear density.

2. A fabric as defined in claim 1 wherein the stretchdirection yarns are crimped composite-filament textile yarns.

3. A fabric as defined in claim 2 wherein the stretchdirection yarns are polyester composite-filament yarns.

4. A fabric as defined in claim 1 wherein the stretch direction yarns are torsionally-crimped textile yarns.

5. A fabric as defined in claim 1 wherein the yarns in the stretch direction have from to crimps per inch.

6. A fabric as defined in claim 1 wherein the yarns in the stretch direction have a crimp development of at least 7. A fabric as defined in claim 6 wherein the nonstretch yarns have a frequency of occurrence of ends per inch of unfinished fabric which is about 200% of the filament crimp frequency in number of crimps per inch of the stretch-direction yarns.

8. A fabric as defined in claim 1 wherein the yarns in the stretch direction are crimped composite-filament yarns and the yarns in the other direction are 30 to 250 denier, 3 to 50 filament, non-stretch yarns of poly(ethylene terephthalate) continuous filaments.

5 (References on following page) 9 10 References Cited FOREIGN PATENTS UNITED STATES PATENTS 199,137 8/1958 Austria.

Great Britain.

3 ig? i 610,140 10/1948 Great Britain.

962 Breen 1 1 172 5 1,033,605 6/1966 Great Britain.

gfig ROBERT R. MACKEY, Acting Primary Examiner. 11/ 1967 Pierce et a1 57140 1. K. CHI, Assistant Examiner. 

